Oscillation generator



Dec. 8, 1925. 1,565,150

J. w. HORTON OSCILLATION GENERATOR Filed July 9'. 1923 Patented Dec. 8, 1925.

UNTED STATES JOSEPH XV. HORTON,

OF BLOOMFIELD. NEVI JERSEY, ASSIGNOR TO WESTERN ELEC- TRIO COMPANY, INCORPORATED, OF NEVI YORK, N. Y., A CORPORATION OF NEW YORK.

OSCILLATION GENERATOR.

Application filed July 9,

To 7l fio/10m t 112.643/ concern.'

Be it known that l, Josnrn: lV. Hormon, a citizen of the United States of America, residing at Bloomfield, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Oscillation Generators, of which the following is a full, clear, concise, and exact description.

This invention relates to oscillation generators and particularly to those employing amplifiers of the space current type.

n object of the invention is to generate oscillations of constant frequency of a higher degree of purity than is obtainable from the usual form of oscillation generator.

f-leretofore, in generating the electrical oscillations, difficulty has been experienced in maintaining` steady oscillations at a fixed and predetermined frequency. The generated oscillations often contain disturbing frequencies such as undesired harmonics of the desired oscillations or slow f'ariations in the frequency of the desired oscillations. The present invention overcomes much of this difficulty and makes it possible to genvcrate oscillations of very constant frequency unaffected by many of the factors which determine the fretjluency in the usual form of oscillation generator.

in accordance with one modification ofthe present invention an oscillation generator, con'iprising a main amplifier having a. regenerative feed back circuit containing an. auxiliary amplifier, is provided with two frequency determining circuits, one inthe input circuit of the main amplifier and the other in the input circuit of the auxiliary amplifier. A step down transformer couples the output circuit of cach amplifier with the input circuit of the other amplifier, thereby tending to reduce the effect of the output circuit impedance of the amplifier upon the frequency determining circuit of the oscillator. A relativelyY low resistance in shunt to the low voltage winding of each step down transformer tends to reduce the 'effect upon the main frequency determining circuit of the transformer impedance or the impedance of circuits associated with the transformer.

ln another' modification ot the invention, two amplifying units are oppositely connected with respect to cach other ill a well 1923, seriaI No. 650,293.

known manner, thereby providing two amplifying paths which are differential with respect to each other, due to the balanced relation of the amplifying units. Two noninterfering feed back circuits are thus possible, and may be employed to provide two noninterfering frequency determining circuits for generating a single frequency or for generating two fundamental frequencies and the combination frequencies of these fundamentals.

Other objects and features of the inventtion are disclosed in further detail in the specification and claims which follow.

Referring to the drawings, Fig. l shows a circuit diagram of an oscillation generator embodying certain features of the invention.

Fig. 2 is a modification of Fig. l.

Figs. 3 and i shows circuit diagrams of oscilla-tion generators making use of oppositely connected amplifying units.

rlhe amplifier 1 includes the amplifying tubes 2, 3 of the well known space current type, each being provided with an anode, cathode and a grid for controlling the space current between the anode and cathode. Amplifier 1 is provided with input circuit 4 and output circuit 5. A regenerative feed back coupling between the output circuit 5 and the input circuit t of amplifier l includes amplifier 6 of similar construction to that of amplifier l. Oscillations are generated by virtue of the fact that energy transmitted from amplifier l is further amplified by amplifier 6 and fed back to amplifier l to cau-se the energy to be still further increased in amplitude.

The amplitude of the oscillations produced by this regenerative action increases until the losses in the circuit Iiust balance the amplification therein. Starting at the output circuit 5, energy is transmitted through amplifier t3, then amplifier l, and back to the circuit 5 from which the energy transmitted through the same cycle of events. For convenience of description, the cycle corresponding to the transmission of a given impulse, once around the regenerative circuit, will be called a cycle of regeneration.

The frequency of oscillations generated is determined by the reactive elements comprising the variable inductance 7 and the variable capacity 8 in the input circuit 1- of amplifier 1 and by the reactive elements comprising the variable inductance 9 and the variable capacity 19 connected between an'iplifier 1 and amplifier 6. Reactive elements 7, 8 constitute a sharply resonant circuit tuned to the frequency of thc waves to be generated. Reactive elements 9, 10 constitute a second sharply resonant circuit tuned to the same frequency as elements 7, S. The effect of providing two resonant frequency determining` circuits of high selectivity is to insure that waves of only one frequency will be generated by the oscillator.

in order to render the tuning,l of resonant circuit 7, 8 as nearly as possible inde iendent of the impedance of circuits closely associated therewith, for example, the output circuit of the amplifier G, a step down transformer 11 is employed for coupling the output circuit of amplifier 6 with the input circuit of amplifier 1. rlhe tuning of reactive elements 7, 8 is rendered still further independent of the impedance of connected circuits by the action of the non-reactive resistance 12 connected in shunt to the low Voltage winding of transformer 11 between said winding' and the reactive elements '5, 8. This resistance is of very low value as compared to the reactance of element or of element S at the frequency of the wave to be generated. For this reason, the damping decrement of the resonant circuit '7, 8, 12 is reduced to a minimum, thus zfdiordinp, *ery sharp tuning. At the same time, the shunt resistance 12 reduces to a substantially negligible quantity, the effect of the inn pedance of transformer 11 upon elements 27, 8. The apparent impedance of transformer 11 may be due to l aliage reactance, capacity between windings, or to the impedance of associated circuits.

rllhe combination of the step-down transformer 11, the shunt resistance 12 of very low Value and tie reactive elements '.7, S, provides a circuit of extremely high selectivity free from the effects of ext 1aneous circuit constants which often interfere with the desired operation of prior types of oscillators. The frequency of the oscillations `generated in the present case is determined largely by the values of the inductance 'l' and the capacity 8. Thevalue of resistance 12 will in any given case be determined by the constants of the tubes to be employed and as a practical example may be of the order of magnitude of .1 to .01 of an ohm ifonc employs a small sized amplifier tube, such as is readily obtainable at the present time in commerce.

rlihe reactive elements 9, 10 are rendered substantially independent of the effects of the impedance of cir-cuits associated ther with by the action of step-down,transiter lvwhieh transmits waves from the our circuit to the amplifier G. Transformer 13 is related to selective circuit 9, 10 in a manner similar to that described in connection with step-down transformer 11 and se lective circuit .7, 8. Non-reactive resistance 14 performs the saine function with respect to selective circuit 9, as resistance 12 plays with respect to selective circuit 7, 8. Amplifiers 1, 6 make up by amplification any loss of energy introduced by the stepdown transforn'ier 11, 13, the resistances 12, 14T, the selective circuits and other portions of the circuit. rllhe load 15 which may be any form of work circuit or circuit to receive waves generated by the oscillator is coupled by means of the winding,T 16 to the output circuit 5. As shown, this winding constitutes an extra winding of the trans former 13, but coul-d obviously be coupled independently ofl transformer 13 to other desired portions )f the oscillator circuit.

The oscillation generator shown in Fig. 2 is similar to that shown in Fig. 1. The oscillator is coupled to the antenna 2O of a radio transmitter. The antenna circuit constitutes one of the resonant circuits which determine the frequency of the oscillations generated and includes the variable inductance 21 and the capacity between the antenna 2O and ground 22. Another resonant frequency determining; circuit, tuned to the same frequency as the antenna, includes inductance 23 and capacity 2li and is separated from the antenna on one side by amplifier 25 and on the other side by ainplifier 26. These amplifiers, due to their unilateral transmission characteristics, permit the separate frequency determining-3T cire cuits to function substantially independently of any reaction by one on the other.

A. feature to be noted in conjunction with Fig. 2 involves a novel method of feeding' baci; energ 1 from the output circuit of amplifi Y r 26 to the input circuitthereof without nialiinp,` use of a transformer employingT two distinct windings is necessary in the usual type transformer coupled oscillator. In order to transmit an impulse from the output circuit of amplifier' 2G to the input circuit thereof, it is necessary for the phase of this impulse to reversed by the feedback coupling. If this be done by the simple and well known expedient of a two winding transformer, the secondary of which gives rise to the desired phase reversal, oscillations of an undesired frequency, usually much higher than those of the desired frepiency, are generated in addition to oscillations of desired frequency, this being due to the resonant circuit formed by the inherent grid-anode capacity within the amplifier tube in conjunction with the inductance of the transformer windings. The system shown in Fig. 2 avoids this difficulty by employing the amplifier, 25 to provide the desired phase reversal of an impulse to be transmitted between the output and input circuits of amplifier 26.

In Fig. 3, the amplifier elements 30, 31 of the well known space current type are connected oppositely with respectto each other, that is, waves transmitted to the grids of tubes and 3l by transformer 32 apply charges of opposite sign at any one instant to the grids of these tubes and produce an amplified response in transforinei 33. faves impressed upon the grids of tubes 30 and 3l by transformer 34 produce charges of like sign upon these grids at any one instant and produce an amplified response in transformer 35. Transformer 32 may accordingly be looked uponas being an input iiansformer for an amplifying path traced through amplifier tubes 30, 3l and terminating in output transformer 33. A second amivilifying path may be traced from input transformer 34 through amplifier tubes 3()l` 3l to output transformer 35. These two amplifying paths are substantially differential with respect to each other due to the well known differential connection between the transformer 34 and the transformer 32 and the diflereiitial connection between the transformer 35 and the transformer 33.

Transformer coupling 33 transmits waves over a feed back circuit 36 to the input cou- ]'iling 34 which .is di tferential with respect to input coupling- 32. lV aves from coupling 34 are amplified by tubes 30, 31 and are tiansinitted in amplified form through coupling 35 and feed back circuit 37 to input coupling 32, then through tubes 30, 3l where the waves are still further amplified and transiixitted back to coupling 33 from which point the cycle of regeneration was traced.

The frequency of the raves transmitted through feed back couplings 36, 37 is deterinined by the sharply resonant circuits 38. 39 andtO, 41 of similar construction, timed to the frequency of the waves to be generated. 'the variable ii'iductance 38 and variable capacity 39 permit of sharp selectivity in transmitting the wave over feed back circuit 36. The effect of impedance in the circuits associated with elements 38, 39 is reduced in a manner somewhat analogous to that described in connection with Fig. l, namely, by making the step-down transformer, while the transformer 34 made a step-up transformer. One or both of the switches 42, 43 may be closed to connect the relatively low nonreactive resistance 44 in shunt to the low .oltage winding of transformer 34 and to connect the relatively low non-reactive resi tance 45 in shunt to the low voltage windii of Vthe transformer Resistances 44 45 are preferably equal in value and 2f. and perform a function similar to that described in connection with resistance 12, Fig. l.

transformer 33 al Nonereactive resistance 46, 47 may be switched in shunt to feed back circuit 37 to function similarly to resistances 44, 45 in feed back circuit 3G. The load 48 is coupled to the windings of transformer 33. It will be noted that each cycle of regeneration in the circuit of F ig. 3 involves two distinct amplifying operations alternated with two distinct selecting operations as in the case of Figs. l and 2.

Fig. 4 employs an arrangement similar to that of Fig. 3, in that oppositely connected amplifier elements 30, 3l are provided with two amplifying' paths which are differential with respect to each other in the manner described in connection with Fig. In Fig. 4, however, it will be noted that waves transmitted from input transformer 50 through amplifier tubes 30, 3l produce amplified waves in output transformer 5l which are transmitted directly back by way of feed back circuit 52 to transformer 50. Sin'iilarly, starting with a wave at input transformer 53, the wave is amplified by tubes 30, 3l and transmitted from the output circuit of the tubes by way of feed back circuit 54 directly to transformer 53.

Variable capaci ty 55 permits of timing the coupling 5t) to resonance with the waves of the frequency to be generated by way of feed back circuit 52. In order to reduce the effec of transformer 5l and circuits associated therewith upon the tuning of circuit 55, 50, an impedance 56, such as a high resistance, maybe .inserted in the feed back circuit between the selective circuit 50, 55 and transformer 5l. Output transformer 57 transmits waves to the two pole double throw switch 58 which, when thrown to the left, causes thc waves to be transmitted to a mechanically resonant frequency indicator which consists of an electron'iagnetically vihrated. bar V59 having a pronounced natural period of vibration to give an audible or visible indication when waves of resonant frequency are applied thereto.

Supposing the switch GO in the feed back circuit t' 2 to be closed and the switch 53 thrown to the left, cai'iacity 55 may be varied until the waves transn'iitted over feed back circuit 52 are of such frequency as to give a resonant indication in the bar 5t). The frequency of oscillations generated is thereby definitely known to be that corresponding to the natural period of the bar 5t) which may be of someV definite standard fre quency. The switch 58 may then be thrown to the right and waves of this standard frequency are then applied to the load or work circuit 61. Y

The switch 60 may then be opened and the switch (52 closed. Variable capacity 63 may then be adjusted to producev resonance with transformers 53, whereby oscillations are generated by virtue of the wavesselectively lli!) transmitted over feed back circuit 5a. The impedance 6i isolates the resonant circuit 53, 63 from the circuits electrically adjacent thereto in a manner similar to impedance 56 in feed back circuit 52. If the switch 58 be thrown to the left and a bar 59 having a different natural frequency from that of the circuit 50, be substituted for the one first used, the capacity 63 may be adjusted until an indication is produced in the bar 59, thereby indicating synchronism between the bar 5f) and Waves being generated by Way of :feed back circuit 5t Switch 58 may then be throivn to the right to supply Waves of this second standard frequency to the load 6l.

In some instances, it is desirable to generate ivaves of such frequency that they may not readily bc produced by a single regenerative feed back circuit, for example, 'very high frequency radio Waves, or Waves of relatively lon7 frequency, such as audio-frequency Waves or sub-audible frequency Waves. ln such cases, the desired Waves may be produced by combining tvvo Waves of different frequency which are readily produced, in order to obtain beat Waves of the desired frequency. This result may be accomplished by means of the circuit shown in Fig. 4, if the circuits 50, 55 ant 53, 63 are first independently tuned to the proper standard frequencies which are to be made to beat together to produce the desired combination frequency. The switches 60, Gl are then simultaneously closed and the beat frequency produced by the tubes 30, 31 may be transmitted by Way of switch 58 to load 6l.

Another method of adjusting the two oscillation frequencies to produce a beat Wave of desired value consists in adjusting one or the other of the resonant circuits 50, 55 or 53, G3 to a standard frequency by comparison ivith a reference standard 59. Another bar 59 of the desired natural period is then substituted for the first bar and the other feed bach circuit of the oscillation generator is closed. The associated variable capacity or 63, as the case may be, is then adjusted until such a frequency is generated that beats of the desired frequency cause an indication in. the bar 59. The switch 58 may then be thrcnvn to thc right to supply the aves of the desired frequency to theV load Gl.

Various modifications of the methods and means disclosed, in connection with the tigures of the drawing will be apparent to one skilled .in the art, and it iS to be understood that the appended claims are .not limited to the precise details shown in the drawings, but broadly set forth novel features of the invention.

lVhat .is claimed is:

l. The method of generating oscillations which 'comprises 'rcgeneratively amplifying oscillations and alternately selecting and amplifying a plurality of times the Wave of generated frequency duringl each cycle of regeneration.

2. An oscillation generator comprising an amplifier having a regenerative feed barn coupling, a plurality of frequency determining means in said feed back coupling, and means between two of said frequency dctermining means to prevent one of said tno means from affecting the other.

3. An oscillation generator comprising a plurality of amplifying devices in tandem, a plurality of frequency determining circuits tuned to resonance at the frequency to be generated, said circuits being intermediate said amplifying devices and separated thereby, the output of the last amplifying devices in the tandem arrangement being coupled to the input of the first amplifying device.

1l. A. translating system including a plurality of translating devices, each having input and output circuits, said devices being so arranged that the output of each transmits to the input of another, and frequency selective means connected between a plurality of said devices, whereby oscillations are generated with a high degree of purity.

5. An oscillation generator comprising an amplifier having a regenerative feed back 'coupling including a reactive network to lecti-vely transmit waves of a given frequency and a nonfreactive resistance in shunt to said reactive network, said resistance being relatively small as compared to the value of said reactance at the frequency of the naves to be generated, whereby the value of said reactance is substantially independent of circuits connected to said coupling on the side of said shunt remote from said reactive circuit.

6. An oscillation generator comprising au amplifier having input and output circuits` a regenerative feed back circuit coupling said circuits including reactive tuningl elements to cause selective transmission of Waves of a given frequency to said input circuit, a step-down transformer coupled bctween said output circuit and said reactive elements, said transformer having a high and a low voltage Winding, a lon' iml'iedancc comicctcd in shunt to said low voltage Winding, said impedance being so small at the frequency to be transmitted by said selective circuit as to render the effect of said trans former upon the timing of said elements substantially negligible.

7. An oscillation generator comprising an amplifier having input and output circuits, a regenerative feed back circuit coupling saidcircuits including reactive timing elements to cause selective transmission of Waves of a given frequency `to said input circuit, a stepfdoivn transformer coupled between said output circuit and said r active llt) elements, an impedance connected in shunt to said feed back Circuit between said transformer and said reactive elements, said impedance being so small at the frequency to be t 1Aansmitted by said selective oireuit as to render the effect of said transformer upon the tuning of said elements substantially negligible.

8. An oscillation generator comprising an amplifier having input und output circuits, a regenerative feed beek circuit coupling said circuits includingl reactive tuning elements to cause selective transmission of Waves of a given frequency to said input eireuit, a step-down transformer coupled between said output circuit and said reactive elements, and a resistance in shunt to said transformer, said resistance being so small as to render the effect of said transformer upon the tuning of said elements substantially negligible.

In Witness whereof, I hereunto subscribe my name this 3 day of July A. D., 1923.

JOSEPH W. I-IORTON. 

